Add the vegetables to saute pan. Cook until brown and slightly softened. Pour vegetables over brisket.

Whisk tomatoes, sugar, stock, and vinegar in a mixing bowl then pour it into same saute pan. Cook for a few minutes to get all flavor out of the pan, then pour over the brisket. Should be at least 3/4 of the way submersed in liquid. Cover dish loosely with aluminum foil and bake for 8 to 10 hours until tender and meat begins to fall apart.